This invention relates to a pressure gauge with a Bourdon tube, more particularly to a pressure gauge which can automatically stop supply of compressed air from a pressure source into an article when the air pressure of the article exceeds a preset value.
The improvement of this invention is directed to the conventional pressure gauge shown in FIGS. 1 and 2. As illustrated, the conventional pressure gauge 10 includes an air chamber 11, a pressure-value indicating panel 12, an adjustment knob 13, a driving lever 14 secured to the adjustment knob 13 so as to rotate synchronously therewith, a driven lever 15 with a fixed upper post 151, a pressure-value indicating pointer 16 for displaying the pressure of the chamber 11, a stop post 17 fastened to and located under the driven lever 15, and a power controlling switch 18 fixed on the panel 12. By rotating the adjustment knob 13 relative to the panel 12, the driving lever 14 impels the driven lever 15 to rotate clockwise to a predetermined position in the gauge 10 which corresponds to a preset upper limit value of air pressure. In a situation where compressed air is supplied from a pressure source into an article whose pressure value is being measured by the gauge 10, when the air pressure of the air chamber 11 exceeds the preset upper limit value, the pointer 16 rotates in the gauge 10 to a position where the pointer 16 contacts the stop post 17 so as to activate the switch 18 to stop the supply of the compressed air from the pressure source into the article. The conventional pressure gauge 10 suffers from the following disadvantages:
(1) The pressure gauge 10 needs a bulky housing to accommodate a large number of parts therein, thereby limiting the applicability of the gauge 10 in industry. PA0 (2) To reduce the preset upper limit pressure value, it is necessary to first pull the adjustment knob 13 upward so as to ascend the driving lever 14 to a level above the upper end of the upper post 151. Then, the adjustment knob 13 is rotated clockwise until the driving lever 14 passes beyond the upper post 151 so that the driving lever 14 can be descended. At this time, the adjustment knob 14 can be rotated counterclockwise to impel the driven lever 15. This adjustment process is time-consuming and troublesome for the user. PA0 (3) Because the adjustment to the preset pressure value is achieved by the operations of the parts 13, 15, 16, 18, when any one of the parts 13, 15, 16, 18 is broken or curved, the gauge 10 may malfunction or cannot display accurately the pressure value of the air chamber 11.